EXTRACORPOREAL SHOCKWAVE THERAPY (ESWT)

"Shock wave" energy radiates through target tissues where they can mechanically stimulate the production of growth factors that are inherently involved in the body's healing and repair functions, including the production of collagen (the most abundant protein in the body). 

Studies have indicated that mechanical loading of tissues increases the expression of several growth factors and cytokines.

These include:

● Insulin-like Growth Factor 1 (IGF-1)
●Transforming Growth Factor-β1 (TGF-β1)
● Interleukin-6 (IL-6)
● Fibroblast Growth Factor-2 (FGF-2)
● TGF-β1
● Platelet Derived Growth Factor (PGDF)

Shockwaves can reduce the levels of a range of cellular substances, messengers, signalling molecules that have important roles in the perception of intense, persistent and chronic pain.

Substance P, for example, is a neurotransmitter that mediates pain information through C type nerve fibers. This protein relays pain messages to the central nervous system and soundwaves generated by shockwave therapy lower the levels of this neuropetide.This in turn reduces the stimulation of pain receptors and can trigger pain relief. 

Shockwave has been shown to improve blood flow through a number of different mechanisms. These include

 ● Production of nitric oxide 

 ● Mechanical stimulation of tissues

The improvement in blood flow has in turn been demonstrated to assist in reduced tension and stiffness of muscles.

We typically divide the inflammatory response into two phases:

● Acute
● Chronic

Acute Inflammation

Acute inflammation is associated with delivery of reparative cells and materials from the blood stream to the site of injury.  The process is a series of biochemical events that is amplifies its response as required.

The process involves

● Local vascular system
● Immune system 
● Cells within the injured tissue
● Neurological system

Shockwave interferes with the production of several of the key inflammatory proteins / mediators (Substance P, Nitric Oxide,  Calcitonin Gene-related Peptide).  For example, shockwave therapy disperses Substance P, which is a neurotransmitter that mediates pain information through the C nerve fibers. The sound waves produced can therefore influence the target cells in the periphery such as mast cells, immune cells and vascular smooth muscle cells, producing heat, swelling, redness and improved healing rate .

Chronic Inflammation

The inflammatory response is a dynamic process and one which requires regulation. Where the inflammation fails to stop it can become the source of further damage.  Think of autoimmune diseases where chronic inflammation results in tissue injury. The process by which inflammation comes to an end occurs by different mechanisms in different tissues.  

In contrast to conditions like rheumatoid arthritis where the inflammatory response is excessive in magnitude or duration, there are many conditions in which the process may be considered to have stalled resulting in a chronic soft tissue complaint. This inflammatory "stall" can be corrected by shockwave.  One example is by mast cell activation. Mast cells play a key role in the inflammatory process delivering key inflammatory mediators able to "kick-start" the inflammatory response.  

These inflammatory mediators include:

Pre-formed mediators (from the granules) 

● proteases, such as tryptase
● histamine (2-5 pg/cell)
● serotonin
● proteoglycans, mainly heparin (active as an anti-coagulant)

Newly formed lipid mediators (eicosanoids):

● thromboxane
● prostaglandin D2
● leukotriene C4
● platelet-activating factor
● cytokines
● eosinophil chemotactic factor

The release of pro-inflammatory mediators through the application of shockwave can help to restore the normal healing and regenerative processes. This allows the process of repair to finish.

Shockwave results in oxidative stress which is where reactive oxygen species (ROS) are produced. ROS are super-reactive molecules containing oxygen and this leads to the production of Nitric Oxide (NO), which is an important cellular signalling molecule.

 NO has a number of important effects:

●Increases in systemic osteogenic factors in  bone  

●Proliferation of new blood vessels 

●Improved blood flow locally 

●Reduction of inflammation